Precision forging methods and apparatus



Feb. 16, 1960 D. A. CAVANAGH 2,925,486

PRECISION FORGING METHODS AND APPARATUS Filed April 14. 1958 4 Sheets-Sheet 1 2h 1 [Fl u 49 yll I x l r 1\\\\ \q FIG.3

In ventor DAN/EL A. CAVANAGH Feb. 16, 1960 D. A. CAVANAGH 2,925,486

PRECISION FORGING METHODS AND APPARATUS Filed April 14, 1958 4 Sheets-Sheet 2 23 PnvP g 23 W H +P; 56 6! Inventor DANIEL A. 'CAVANAGH by." M M Feb. 16, 1960 D. A. CAVANAGH 2,925,436

PRECISION FORGING METHODS AND APPARATUS Filed April 14, 1958 4 Sheets-Sheet 3 64 szuh EQQQ/EEIG 65 as 59 s2 7 s7 ey 70 68 T 53 60 Inventor DANIEL A. CA VANA GH MJ W Feb. 16, 1960 D- A. CAVANAGH 2,925,486

PRECISION FORGING METHODS AND APPARATUS FilOd April 14 1958 4 Sheets-Sheet 4 FIG. 9

I 99 707 as 86 9 77 Inventor DAN/EL A. CAVANAGH nited States Patent PRECISION FORGING METHODS AND APPARATUS Daniel Alfred Cavanagh, Warren, Ohio Application April 14, 1958, Serial No. 728,326

14 Claims. (Cl. 219-151) This invention relates to methods and 'apparatus for forming precision forgings in one forging and heating operation, and in which a forging die is maintained electrically isolated in an electrical 'heatingcircuit during heating and forging operations.

This application is a continuation in part of my application Serial Number 548,483, filed November 22, 1955, now Patent No. 2,836,706, for Precision Forging Method and Apparatus.

Conventional mechanical forging machines may be used to produce precision forgings by striking induction or flame heated bar stock into a precision die. A substantial temperature drop occurs during the transfer of v the heated bar stock from the heating apparatus, whether of the induction, gas or resistance heating type, to the forging press which embodies the forging die. Allowance must be made for this characteristic in heating the bar stock to a temperature sufficiently above the desired forging temperature to avoid undue cooling during transfer necessarily giving rise to grain growth. During stock transfer from the heating step to the forging operation, surface oxidation or scale forms to a degree limiting consistent reproduction to close tolerances and causing a high rate of wear in the forging die. Generally, therefore, precision forgings are accomplished by means of progressive forging operations employing a number of dies and a number of separate heating and forging operations except in cases where the amount of material being gathered and forged is very small. In many cases, the final forging operation comprises cold striking to attain finishing dimensions.

In any forging operation, temperature control is of utmost importance. In the case of precision forging methods, a variation in forgng temperature can cause variation in dimension beyond permissible tolerances. The heating step may be carefully controlled and yet during transfer to the forging operation, the bar stock may be subjected to unpredictable variables affecting the forging temperature to such an extent that the percentage of rejects is unduly high. The term precision forging as applied in the art heretofore merely signifies an attempt to forge to such tolerances that little or no machining is required thereafter though removal of die seam flash by shearing is generally accepted.

It is the main object of this invention to provide a method and apparatus for precision forging in which electrical resistance heating of the bar stock to be forged is accomplished while the stock is in a die and the die is maintained electrically isolated.

It is a further object of the invention to provide a method and apparatus for precision forging on production runs of large quantity with a low percentage of rejects due to causes other than temperature control.

It is a still further object of the invention to practice temperature control by means of a stock gathering operation under predetermined hydraulic or pneumatic pressure while a predetermined electrical current flows through the stock to develop a stock upset at a specific forging temperature and to immediately forge said upset to a precision shape at a specific and different forging pressure.

It is a still further object of the invention to provide a method and apparatus for heating bar stock or the like in a forgeable region thereof to a forging temperature and immediately upon cessation of said heating step, forging the forgeable region to a precision shape to form a substantially flashless forging.

It is a still further object of the invention to provide a method and apparatus for forging materials heretofore considered as non-forgeable and substantially any metal having a detectable plastic range and as short as twentyfive degrees Fahrenheit and shorter, such as, for example, cold working metals and alloys, difiicult titanium alloys and high temperature metals and alloys of the recent metal arts. It is a still further object of the invention to provide a method and apparatus for forming precision forgings in a die formed of conventional die material, wherein the bar stock or workpiece is heated by electrical resistance heating techniques.

With these and other objects in view, the invention will be appreciated by a study of the following specification taken in conjunction with the accompanying drawings.

In the drawings:

Figure 1 is a plan view of a preferred form of precision forging apparatus according to the invention;

Figure 2 is an elevation of the apparatus of Figure 1 embodying a schematic layout of hydraulic and electrical controls therefore;

Figure 3 is a perspective view of a precision forging, which may be formed according to the invention in effectively one machine operation;

Figure 4 is a diagrammatic sectional View illustrating the method of the invention diagrammatically showing the location of the operative components at the beginning of a heating, stock gathering and forging cycle;

Figure 5 illustrates a material upset formed by gathering of bar stock according to the invention under a stock gathering pressure P at the moment of application of additional pressure P Figure 6 illustrates the formed by stock die;

Figure 7 is a diagrammatic illustration of double ended forging apparatus according to the invention, in which both ends of a workpiece may be forged simultaneously, and wherein current balancing means of the invention are incorporated.

Figure 8 is a transverse sectional view of a specific form of brush contacting mechanism of the invention disclosing electrical contact over an entire circumferential surface of the bar stock workpiece being forged.

Figure 9 is a sectional view of anvil transfer mechanism utilized in providing a forging anvil for a forging stroke shiftable into place upon predetermined upsetting of material to form a valve.

Figure 10 is a sectional view of the portion of the apparatus illustrated in Figure 9 showing the anvil or ram in the withdrawn position.

Figure 11 is a face elevation of the shiftable anvil heads on the'ram of the invention illustrating the mechanism for shifting the same.

Referring to the drawings, a machine bed 10 having an abutment block 11 slidably supports a forging die 12 movable axially by means of the cross bars 13 thereof under action of the pistons 14 of .the parallel spaced apart hydraulic cylinders 15 fixed on the machine bed. The die 12 is separable and embodies the upper and lower parts or jaws 16 and 17 which may be firmly held together by means of suitable bolts 18 or other high presprecision forging of the upset gatherings as shown in Figure 5 into a 3 sure clamping means manually or hydraulically actuated in accordance with well known mechanical principles and methods. A lengthof bar stock 19 or the like rests in the lower part 17 of the die 12 and is held therein under suitable clamping pressure by means of the clamping bolts 18 described, pressing the upper part 16 of the die into firm engagement therewith. The die 12 embodies a precision cavity into which a portion of the bar stock 19 is to be gathered and forged. An electrical contacting brush 20 makes electrical contact with the bar stock 19.

The bar stock 19 initially projects beyond the die 12 for engagement of the contact end 21 thereof by an anvil block or head 22 supported by piston 23 of hydraulic pressure cylinder 24 supported by the machine bed 16. The anvil block 22 is connected to a source'25 of alternating current as is the contact brush 20 fromwhich it is insulated in any suitable way, to cause electrical resistance heating of that portion of the bar stock 19 referred to herein as the forgeable region 26 extending between the contacting brush 20 and the anvil 22. A suitable switch 27 is actuated to control the application of heating current to the forgeable region 26.

The method of the invention is illustrated in Figures 4 to 6 wherein like numerals indicate like components.

Referring also to Figure 2, the bar stock 19 is first supported in any suitable way between the anvil 22 and 'the abutment 11 under a predetermined axial hydraulic pressure P, effecting electrical contact between contact surfaces 28 of the anvil and the contact end 21 of bar stock 19. A second electrical contact is made to the bar stock by means of the contact brush 20 shown in Figures 4 to 6 having a brush element 29 preferably formed of hard copper or the like and acting under pressure of a spring 30 or other suitable means such as an hydraulic pressure device (not shown) and connected to source 25 and switch 27 substantially as shown. In Figure 4, the brush 29 is initially spaced a relatively short distance D,, from the contact end 21 of the bar stock and is insulated from head 22 by insulation 55. It is preferred that the distance D be initially a minimum so that a fast heating ofthe forgeable region 26 will be accomplished by flow of electrical current from the source 25 through a minimum electrical resistance upon closure of switch 27.

According to the invention, the temperature at which stock gathering occurs is dependent upon hydraulic pressure P as hereinafter set forth in more detail. Thus, as heating of-the forgeable region 26 increases, the anvil or head 22 will remain substantially stationary until the material of the forgeable region attains a temperature at which the material under pressure P yields and begins gathering. By this method and means, the stock gathering temperature can be controlled in a precise manner by control of the pressure P to a predetermined value. The lower the pressure P the higher the stock gathering temperature. The pressure P is therefore that controlling the stock gathering temperature to a value adapted for an immediately following forging step.

As the forgeable region 26 attains a temperature sufficient to permit stock gathering, i.e., the particular temperature-yield pressure point in plastic temperature range has been achieved, the anvil 22 advances under the ram pressure P for such particular temperature to effect an enlargement or upset 31. During the stock gathering operation, current flow is maintained through the forgeable region of the bar stock. It will also be observed that as the stock gathering operation proceeds, the length of the forgeable regionis substantially maintained by advancing the brush 29 over the bar stock 19. The brush 20 is moved along the bar stock from the moment at which current flow begins to provide fresh and efl"1 cientelectrical contact during the electrical heating step and to avoid undue heating of'the brush contacting surfaces. The anvil head 28 does not move from the position illustrated in Figure 4 until the forgeable region has attained a temperature at which stock gathering can begin under action of the predetermined stock gathering pressure P The brush 29 may be supported by a separate carrier (not shown) or the die 12. As shown in Figures 1 and 2, the die is located between the brush contact and anvil 22. It is significant that during the stock gathering'operation, the die precisely controls the contours of the neck portion 32 of the upset being formed.

As shown in Figure 2, the hydraulic fluid pumps 33 and 34 delivering hydraulic fluid under pressure from fluid sump 35 connect to the double two-way valve 36 by means of which the anvil head 22 is movable under the pressure Pi for stock gathering when the forgeable region attains a stock gathering temperature. The die including the brush 29 is movable toward the abutment 11 under action of the hydraulic cylinders 15' at pressure P as modified by the valve 37 which may be of the restriction type whereby the rate of advance of the die and brush 29 may be controlled. By this means, the shape of the upset 31 formed in the stock gathering operation can be controlled to suit the form necessary for the subsequent forging operation to precision tolerance in the die cavity 38. The rate of advance of the die 12 as controlled by the valve 37 will determine the final spacings ranging between values S and S shown in Figure 5 between the anvil face 28 and the die at the conclusion of the stock gathering operation. The simultaneous opening of switch 27 and support of die 12 in a stationary position for support of the bar stock during the immediately following forging operation may be accomplished by means of a number of well-known mechanisms operating in accordance with this disclosure in the manner suggested in Figure 2. Thus, as the die 12 arrives at its limiting position of motion, in this case against the abutment 11, actuating mechanism 39 of any suitable form operatively connected to both switch 27' and high pressure valve 4! controlling the outlet of pump 34, is engaged by the die to cause switch 27 to open, thereby effecting cessation of electrical current flow through the bar stock and simultaneously opening valve 40 causing hydraulic pressure applied against the anvil head 22 to be increased by additional pressure P to predetermined value.

The cessation of current flow and preferably simultaneous increase of pressure, mark the beginning of the forging step or stroke of the anvil head22 during which the gathered material represented by the upset 31 while at substantially ideal forging temperature, is forced into the die cavity 38 to form in one forging operation, the final precision forged product 41 shown also in Figure 3. The mechanism may be returned to the initial position illustrated in Figures 1 and 4 by turning valve 36 for reverse action of the hydraulic cylinders and since in the reversing action the anvil head 22 will be drawn away from the die 12, closure of switch 27 will be accomplished while the anvil head is removed from contact with the finished upset article 41. Moreover, upon closure of switch 27, the valve 40 is closed where by the mechanism is returned to the initial position'under action substantially of the pump 33 alone.

It must be borne inmind that in any stock gathering operation according to the invention, it is desired to attain a temperature which is suitable for an immediately following forging operation. Since the stock gathering'operation is accomplished under hydraulic pressure, the correct hydraulic pressure to be applied will be that corresponding to the pressure necessary to deform the material at the deforming or stock gathering temperature. The pressure necessary to cause plastic flow will depend upon the temperature.

For example, assuming it is desired to accomplish the die forging step at 2,000 F., thenthe initial stock gathering pressure should be sufliciently low that stock gathering will not begin until the forgeable region has attained atemperature of 2,000" F. If this initial pressure were greater, stock gathering would begin at a lower temperature and then the formed upset would not be at a sufficiently high temperature to undergo successful precision forging into the die cavity in the latter step of the method. It will be evident, therefore, that the stock gathering pressure is used according to this invention as a temperature control determining both the stock gathering temperature and the temperature at which the following die forging operation proceeds. One first determines the forging temperature required from which the pressure P can be determined.

It has been found impractical to maintain electrical current flow through the bar stock in the last die forging step of the method herein in the case of the formation of a part such as the die forging 41 having a slightly bulged finished edge 42 because the anvil face 28 and the die arrive in such close proximity that electrical current flow therebetween through a small portion of the workpiece or bar stock therebetween may cause excessive beating or other damage to the anvil face 28 or the die or both, as well as to the workpiece or forging The invention permits the use of ordiary die materials for the forging die and ordinary materials for the anvil face rendering impractical the use of high cost high resistance low thermal conductivity die materials made necessary if current flow is maintained during forging stroke. Therefore, the severance of electrical current flow before the completion of the die forging operation is preferred and will be found to be highly practical in nearly all cases.

While a single contact brush has been disclosed for purposes of convenience in Figures 1 to 6, the use of a single brush contact may be impractical due to nonuniform current flow in many precision forging operations. It is therefore preferred to provide contact about an entire circumferential area of the workpiece as shown in the case of workpiece 43 shown in Figure 8. Copper brushes 44 supported by holders 45 slidable radially and connected by flexible leads 46 to electrode 47 of the electrical current supply system (not shown). Holders 45 are actuated by hydraulic cylinders 48 mounted on carrier plate 49 to effect contact of brushes 44 under substantial pressure with workpiece 43. The brushes are moved along the workpiece by movement of the carrier plate 49 and the assembly shown with the forging die or independently. The brushes are separated by an angleof one hundred and twenty degrees in the arrangement shown. Applicant has established that more than two brushes should be used to provide efficient circumferential contact.

Die isolation According to this invention the forging die structure is maintained in electrically isolated condition in the electrical resistance heating circuit which latter includes the bar stock adapted to be heated while supported within the die itself. Thus, referring again to Figures 4 to 6 and 8, it will be observed that the electrical contacting brush 29, spring 30 and terminal cap 50 are electrically insulated by insulation 51 from the die structure 12. Preferably the brush terminal 50 is connected to the grounded side of the electrical power source 25 shown grounded as at 52. By this means electrical current flow through the bar stock 19 is confined to the shortest physical path through the bar stock between the anvil face 28 engaging the bar stock contact end 21 and the contact brush 29. The die structure 12 is therefore isolated from the contacting brush structure 20 and in addition is electrically isolated from the machine bed or frame 54 by insulation 55. Likewise, the ram head 22 is electrically isolated from the bed or frame 54 by insulation 55.

In operation therefore, during the transitory retraction of the die structure 12 to the position indicated in Figure 5, any enlargement of the. bar stock due to upsetting pressure in the region of the necked portion 56 of the die causing contact of bar stock material with surfaces of the die will not give rise to flow of electrical current into the die since the preferential shortest path fo'r current flow is through the bar stock to the contact face 53 of brush 29'.

Adherence to the desire to electrically isolate the die according to the invention is assisted by the specific brush structure disclosed in Figure 8 in which the brush holders 45 are encased within rigid tubular sleeves 57 formed of electrical insulation material. A die which floats electrically in the resistance heating electrical circuit is intended to be used in the various apparatus arrangements illustrated in this application whether the apparatus is of double ended or single ended construction. Thus, while an illustration has been given of apparatus for forging one end of a length of bar stock simultaneous forging of both ends may be accomplishedin similar fashion in the manner disclosed in Figure 7.

Simultaneous double ended forging In the double ended forging apparatus of the invention illustrated in Figure 7, it is to be understood that the requirements for electrical die isolation and other insulation requirements according to this invention are followed.

In Figure 7 a machine bed 58 fixedly supports the opposed double acting hydraulic ram cylinder 59 and 6t) co-axially aligned and having ram heads 60 and 61 respectively carrying electrical resistance heating transformers 62 and 63 therefor. In this figure the transformers indicated by T are shown schematically thereabove, and are designated by numerals 62a and 63a connected in parallel to a common source 64. Accordingly, it will be understood that the transformers may be physically carried by the ram heads 60 and 61, but that the electrical circuitry follows that indicated by the electrical schematic portion of the figure. It is a feature of the invention that the final electrical resistance heating loads of the transformer 62a and 63:: be balanced by the adjustable shunts 65 and 66 respectively, whereby to obtain the same consumption of heating energy for both ends 67 and 68 of the bar stock 69 simultaneously. Assuming both ends of the bar stock to be of the same dimensions, and the upset to be formed thereon of the same material volume, adjustment may be made in the shunts to maintain an identical heating rate at both ends of the bar'stock. On the other hand, if the volume to be heated is different at one end than at the other, adjustment may be made by means of the shunts to equalize the heating rates. By this means uniform heating rate may be accomplished at both ends simultaneously.

The bar stock 69 is held between the ram heads 60 and 61 and clamped relative to the machine bed by means of a separable clamping structure 70 of any suitable form. It is preferred that some kind of intermediate clamp be provided since in the double ended forging apparatus according to the invention, the bar stock should not initially be in physical contact with surfaces of the die. The forging dies 71 and 72 shown are of a separable kind in order to permit removal of the bar stock 69 from the apparatus.

It will be assumed in the disclosure with reference to Figure 7 that the dies 71 and 72 embody insulated brush structures for making electrical contact to the bar stock; that the die is electrically isolated and movable as desired as disclosed in Figures 1, 2 and 4 to 6; that the ram head 60 is electrically insulated from the machine bed 58 and that the die contact brush is grounded as is the machine bed. It will also be assumed that the hydraulic circuitry "73 revealed only in the most elementary form accompanies the functions of the hydraulic circuitry in Figure 2 described.

Dual forging head It has been found that the precision forging of some materials such as some hard special steels of the high thermal damage resistance class are difiicult to contact electrically and to forge with the same ram head contact face material. The provision of a replaceable forging head part supported by the ram head is only partial solution to the problem because of the wear characteristics which can result due to temperature stresses and the like which may arise. These disadvantageous character istics are vastly increased if the contact end of the bar stock is not finished sufficiently smoothly, preferably by grinding to provide what would ordinarily be regarded as a suitable electrical contact surface. stances, grinding cut-off apparatus may be available for cutting the bar stock to the desired length. A shear cut stock may cause excessive damage on contact to the ram forging head part. While to some extent the damage caused and the poor efiiciency of contact on sheared stock can be overcomeby changing the heating current by means of current pulses effecting a minute puddling and melting of the sheared contact face of the bar stock in a manner well known in the application of current pulses for starting welding electrodes and similar welding techniques, and while it may be understood that the power source then may embody such current pulsing, it has been evident nevertheless, that a sheared bar stock end of high temperature steels in particular, is so highly damaging to a ram forging head part surface as to impose requirements for the material thereof rendering the same impractical fo'r an electrical contacting surface.

The invention therefore provides for the utilization of two ram heads, one of which is formed of a material especially suited for efiicient electrical contact with the bar stock material being worked. This material should be suitable for effecting some deformation or upsetting of the bar stock occurring during heating. The forging stroke however, is accomplished according to the invention, with a ram forging head material of desirable structural characteristics for the high pressure forging stroke. Thus in Figures 9 to 11, the machine bed 74 having the hydraulic ram cylinder 75 isolated but supported by insulation 76 thereon, carries a die holder 77 insulated as at 78 and supporting a die mount 79 and die 80 in t axial alignment with the ram cylinder 75. The ram head 81 carries a forging head guide plate 82 insulated there from by insulation 83 and preferably transversely slidably supporting a forging head carriage 84 fixedly mounting the forging heads 85 and 86. Insulated brush contact means 87 are adapted to make electrical contact with bar stock supported in the die head bore 88, as indicated in Figure 10. The bar stock 89 is initially contacted by the contact head 85 preferably formed of a material such as beryllium copper alloy, the latter being-in electrical contact with the carriage 84 connected by lead 90 to energizing transformer 91, the other lead 92 of the output winding 93 of the transformer serving brush 87 which may be grounded as at 94. Preferably the die mount 79 embodies cooling passages 95. Cooling passages 96 are also preferably provided in the ram head structure particularly in the forging head abutment portion 97 thereof, as indicated by numeral 98.

The forging-head guide plate 82 carrying the hydraulic cylinder 99 as shown in Figure 11 advances towards the die 80 to effect contact of the contact head 85 initially with the bar stock 89. When the heating cycle is completed, accomplished preferably by some upsetting func- In some intion, the ram head is retracted slightly by manual con- Summary The method of the invention, however makes practical the production of precision forgings (dimensional control within .005 in/ in.) without flash in full automatic equipment by combining resistance heating of the material with gathering of the material by means of pressure from a hydraulic ram, followed by forging the hot gathered material into a die.

In the automatic precision electric forging of brass according to the method of the invention, the die and brushes are grounded to the frame of the machine and the heating or contact head is insulated from the machine frame. A standard type of .30 carbon hot die steel hardened to 45 Rockwell C is suitable for forging brass. It can be shown that the relatively high electrical resistance of hardened die steel compared to brass reduces the electric current flow through the die as compared to that through the brass to a practical low value. When making steel forgings in the same apparatus however, the relative current flow through the die is so high as to cause welding of the forging to the surface of the die. This is corrected according to the invention by insulating the die or die holder from the frame of the machine thereby preventing electrical current flow through the die.

Insualting the die holder and hence the die from the frame of the machine allows a choice of die material to be made without restrictions of electrical resistance value. Hence materials such as full hard berryllium copper or other non-magnetic high heat conductivity materials may be used which when kept water cooled have excellent dimensional stability and wear properties for hot forging of steels and other metals.

Because of the position of the die in the electric circuit of the machine it heats up considerably due to an inherent induction heating effect if the die is made from magnetic material. As a result the dimension of the forged part varies with production rate when using a magnetic die material. The variation is not objectionable in some cases. However, in order to make precision forgings with dimensions independent of production rate it has been found to be preferable to use a nonmagnetic hardened die in a non-magnetic water cooled die holder insulated from the frame of the machine.

What I claim as my invention is:

1. The method of forming a finished forging from a work piece in one combined heating and forging operation, in a die having die cavity surfaces defining the shape of the forging produced and comprising the steps in combination of: heating said work piece with a source of electrical current by electrically contacting said work piece at spaced apart contact areas therealong to effect heating of at least a portion thereof to forging temperature; during heating of said work piece, at least partially surrounding said portion by said die cavity to dispose the die surfaces thereof in surrounding spaced relation thereto; during'heating of said work piece, electrically isolating said die from said source; severing the flow of electrical heating current from said source through said work piece when the said portion of the latter attains a forging temperature; and immediately upon said severance of current, forging said work piece portion with a forging pressure to effect deformation thereof providing engagement of said portion with said die surfaces thereby to form said forging defined by said die cavity.

2. The method of forming a finished forging from a work piece in one combined heating and forging operation in a die having die cavity surfaces defining the shape of the forging produced and comprising the steps in combination of: heating said work piece with a source of electrical current by electrically contacting said work piece at spaced apart contact areas therealong to effect heating of at least a portion thereof having a volume corresponding to that of said cavity to forging temperature; during heating of said work piece at least partially surrounding said portion by said die cavity to dispose the die surfaces thereof in surrounding spaced relation thereto; during heating of said work piece, electrically isolating said die from said source; severing the flow of electrical heating current from said source through said work piece when the said portion of the latter attains a forging temperature; and immediately upon said severance of current, forging said work piece portion with a forging pressure to effect deformation thereof providing engagement of said portion with said die surfaces thereby to form said forging defined by said die cavity.

3. The method of forming a finished forging from a work piece in one combined heating and forging operation in a die having die cavity surfaces defining the shape of the forging produced and comprising the steps in combination of: heating said work piece with a source of electrical cur-rent by electrically contacting said work piece at spaced apart contact areas therealong to effect heating of at least a portion thereof to forging temperature; during heating of said Work piece at least partially surrounding said portion by said die cavity to dispose the die surfaces thereof in surrounding spaced relation thereto; during heating of said work piece, locating one of said electrical contact areas on said work piece within said die cavity; during heating of said work piece electrically isolating said die from said source, effecting a preferential flow of heating current through said work piece and confining heating current thereto; severing the flow of electrical heating current from said source through said work piece when the said portion of the latter attains a forging temperature; and immediately upon said severance of current forging said work piece portion with a forging pressure to effect deformation thereof providing engagement of said portion with said die surfaces thereby to form said forging defined by said die cavity.

4. The method of forming a finished forging from a work piece in one combined heating and forging operation in a die having die cavity surfaces defining the shape of the forging produced and comprising the steps in combination of: heating said work piece with a source of electrical current by electrically contacting said work piece at spaced apart contact areas therealong to effect heating of at least a portion thereof having a volume corresponding to that of said cavity to forging temperature; during heating of said work piece, at least partially surrounding said portion by said die cavity to dispose the die surfaces thereof in surrounding spaced relation thereto; during heating of said work piece locating one of said electrical contact areas on said work piece within said die cavity; during heating of said work piece, electrically isolating said die from said source, effecting a preferential flow of heating current through said work piece and confining heating current thereto; severing the flow of electrical heating current from said source through said work piece when the said portion of the latter attains a forging temperature; and immediately upon said severance of current forging said work piece portion with a forging pressure to effect deformation thereof providing engagement of said portion with said die surfaces thereby to form said forging defined by said die cavity.

5. The method of forming a finished forging from a work piece in one combined heating and forging operation in a die having die cavity surfaces defining the shape of the forging produced and comprising the steps in combination of: heating said work piece with a source of electrical current by electrically contacting said work piece at spaced apart contact areas therealong to effect heating of at least a portion thereof to forging temperature; during heating of said work piece, at least partially surrounding said portion by said die cavity to dispose the die surfaces thereof in surrounding spaced relation thereto; during heating of said work piece locating one of said electrical contact areas on said work piece within said die cavity; during heating of said work piece, electrically isolating said die from said source, effecting a preferential flow of heating current through said work piece and confining heating current thereto; during heating electrically grounding said source and said contact area within said die cavity; severing the flow of electrical heating current from said source through said work piece when the said portion of the latter attains a forging temperature; and immediately upon said severance of current, forging said work piece portion with a forging pressure to effect deformation thereof providing engagement of said portion with said die surfaces thereby to form said forging defined by said die cavity.

6. The method of forming a finished forging from a work piece in one combined heating and forging operation in a die having die cavity surfaces defining the shape of the forging produced and comprising the steps in combination of: heating said work piece with a source of electrical current by electrically contacting said work piece at spaced apart contact areas therealong to effect heating of at least a portion thereof having a volume corresponding to that of said cavity to forging temperature; during heating of said work piece, at least partially surrounding said portion by said die cavity to dispose the die surfaces thereof in surrounding spaced relation thereto; during heating of said work piece, locating one of said electrical contact areas on said work piece within said die cavity; during heating of said work piece, electrically isolating said die from said source, effecting a preferential flow of heating current through said work piece and confining heating current thereto; during heating electrically grounding said source and said contact area within said die cavity; severing the flow of electrical heating current from said source through said work piece when the said portion of the latter attains a forging temperature; and immediately upon said severance of current, forging said work piece portion with a forging pressure to effect deformation thereof providing engagement of said portion with said die surfaces thereby to form said forging defined by said die cavity.

7. Precision forging apparatus adapted to forge a metal work piece in one heating and forging cycle and comprising in combination: means for passing electrical energy from a current source through at least a portion of said work piece; a forging die having a die cavity; means supporting said die to dispose the die cavity thereof in adjacent spaced relationship about said work piece portion; means insulating said die from said source except upon contact of said work piece with said die providing confinement of current flow through said work piece during heating of the latter; means for severing the flow of electrical current through said work piece portion when the latter attains a forging temperature; and means responsive to said current severing means for forging said work piece portion while at forging temperature into said die cavity to form a forged shape defined by said die cavity.

8. Precision forging apparatus adapted to forge a metal work piece in one heating and forging cycle and comprising in combination: means for passing electrical energy from a current source through at least a portion of said work piece; a non-magnetic forging die having a die cavity; means supporting said die to dispose the die cavity thereof in adjacent spaced relationship about said work piece portion; means insulating said die from said source except upon contact of said work piece with said die providing confinement of current flow through said work piece during heating of the latter; means for 11 severing the flow of electricalcurrent through said work piece portion when the latter attains a forging temperature; and means responsive to said current severing means for forging said work piece portion while at forging temperature into said die cavity to form a forged shape defined by said die cavity.

9. Precision forging apparatus adapted to forge ametal Work piece in one heating and forging cycle and comprising in combination: means for passing electrical energy from a current source through at least a portion of said Work piece; a forging die having a die cavity; means supporting said die to dispose the die cavity thereof in adjacent spaced relationship about said work piece portion; means insulating said die from said source except upon contact of said work piece with said die providing confinement of current flow through said work piece during heating of the latter; means for severing the flow of electrical current through said work piece portion when the latter attains a forging temperature; an hydraulic ram having a ram head; an anvil part on said ram head engageable with said work piece for effecting passage of electrical current into said Work piece portion; means in said ram head for accommodating a coolant to control the temperature of said anvil part; and means responsive to said current severing means for moving said ram head under forging pressure to effect forging of said work piece while at forging temperature into said die cavity to form a forged shape defined by the cavity of said die.

10. Precision forging apparatus adapted to forge a metal work piece in one heating and forging cycle and comprising in combination: means for a passing electrical energy from a current source through at least a portion of said work piece; a non-magnetic forging die having a die cavity; means supporting said die to dispose the die cavity thereof in adjacent spaced relationship about said work piece portion; means insulating said die from said source except upon contact of said work piece with said die providing confinement of current fiow through said work piece during heating of the latter; means'for severing the flow of electrical current through said work piece portion when the latter attains a forging temperature; an hydraulic ram having a ram head; an anvil part on said ram head engageable with said work piece for effecting passage of electrical current into said work piece portion; means in said ram head for accommodating a coolant to control the temperature of said anvil part; and means responsive to said current severing means for moving said ram head under forging pressure to effect forging of said work piece while at forging temperature into said die cavity to form a forged shape defined by the cavity of said die.

. 11. Precision forging apparatus adapted to forge a metal work piece in one hetaing and forging cycle and comprising in combination: means for passing electrical energy from a current source through at least a portion of said work piece; a forging die having a die cavity; means supporting said die to dispose the die cavity thereof in adjacent spaced relationship about said work piece portion; means insulating said die from said source except upon contact of said work piece with said die providing confinement of current flow through said work piece during heating of the latter; means for severing the flow of electrical current through said work piece portion when the latter attains a forging temperature; an hydraulic ram having a ram head; an anvil part on said ram head engageable with said work piece for effecting passage of electrical current into said work piece portion;

means in said ram head for accommodating a coolant to control the temperature of said anvil part; a transversely movable shifting support for said anvil part mounting the latter on said ram head; a separate forging anvil part mounted in laterally spaced apart relation from said first anvil part on said support; means laterally shifting said support efiecting replacement of said first anvil part by said forging anvil part after severance of curent flow through said work piece and while said portion is at forging temperature; and means energizing said ram head under a forging pressure, after engagement of said work piece portion while remaining at forging temperature with said forging anvil part, effecting forging of said work piece portion into said die to form a forging shape de fined by said die cavity.

12. Precision forging apparatus adapted to forge a metal work piece in one heating and forging cycle and comprising in combination: means for passing electrical energy from a current source through at least a portion of said work piece; a non-magnetic forging die having a die cavity; means supporting said die to dispose the die cavity thereof in adjacent spaced relationship about said work piece portion; means insulating said die from said source except upon contact of said work piece with said die providing confinement of current flow through said work piece during heating of the latter; means for severing the flow of electrical current through said work piece portion when the latter attains a forging temperature; a hydraulic ram having a ram head; an anvil part on said ram head engageable with said work piece for effecting passage of electrical current into said work piece portion; means in said ram head for accommodating a coolant to control the temperature of said anvil part; a transversely movable shifting support for said anvil part mounting the latter on said ram head; a separate forging anvil part mounted in laterally spaced apart relation from said first anvil part on said support; means laterally shifting said support effecting replacement of said first anvil part by said forging anvil part after severance of current flow through said work piece and while said portion is at forging temperature; and means energizing said ram head under a forging pressure, after engagement of said work piece portion while remaining at forging temperature with said forging anvil part, effecting forging of said work piece portion into said die to form a forging shape defined by said die cavity.

13. Precision forging apparatus adapted to simultaneously forge a straight bar-like work piece in separate forgeable regions thereof in one heating and forging cycle and comprising in combination: means for passing electrical energy from a current source through at least both said forgeable regions of said work piece; two forging dies each having a die cavity; means supporting said dies to dispose the cavities thereof in adjacent spaced relationship about said forgeable regions; means insulating said dies from said source except upon contact of said work piece with each die providing confinement of current flow through said work piece during heating of the latter; means for simultaneously severing the flow of electrical current through said forgeable regions when the latter attain substantially the same forging temperature; and means responsive to said current severing means for forging said work portions while at forging temperature simultaneously into said die cavities to form forged shapes on said workpiece defined by said cavities.

14. The method of forming a finished forging from a straight bar work piece in one combined heating and forging operation in two axially spaced apart dies each having die cavity surfaces defining the shape of the forging effected on the work piece and comprising the steps in combination of: heating said work piece with a source of electrical current by electrically contacting the work piece at spaced apart contact areas therealong to effect heating of at least two portions thereof to forging temperature; during heating of said work piece, at least partially surrounding each of said work piece portions.

by one of said die cavities to dispose the die surfaces of the latter in surrounding spaced relation thereto; during heating of said work piece, electrically isolating said die from said source; severing the fiow of electrical heating current from said source through said work piece portions when the latter attain substantially the same forging temperature; and immediately upon severance of said electrical current, forging said work piece portions with forging pressures efiecting deformation thereof, providing engagement of each of said portions with the die surfaces of the die associated therewith thus efiecting simultaneous forging of two portions of said work piece to a form defined by the cavities of said dies.

Thomson Jan. 8, 1889 Lauder et a1. Sept. 30, 1890 14 Rietzel Mar. 7, Murray Mar. 12, Giacchino Aug. 5, Drake Aug. 9, Frost Apr. 16, Sciaky Oct. 8, Finzel Apr. 12, Grimes July 30, Knight Aug. 4, Knight Jan. 5, Aeckersberg et a1. Jan. 26, Fleischrnann Dec. 10, 

